(1) Field of the Invention
The present invention relates to a treating tank for treating substrates as immersed in a treating liquid, and a substrate treating apparatus having the treating tank. More particularly, the invention relates to an improvement in treating liquid injection pipes attached to the treating tank.
(2) Description of the Related Art
This type of treating tank requires streams of a treating liquid to be formed therein. For this purpose, as shown in FIGS. 1A through 1C, a treating tank 110 includes treating liquid injection pipes 103 disposed adjacent the bottom thereof. Each injection pipe 103 has a closed distal end 100, and numerous treating liquid jet bores 102 arranged along a side wall for jetting a treating liquid introduced through a proximal end 101 out into the treating tank 110. Conventionally, as shown in the drawings, each injection pipe 103 is formed of a single pipe having a constant inside diameter id from the proximal end 101 to the distal end 100. The jet bores 102 formed in each injection pipe 103 have the same cylindrical shape and size. These bores 102 are formed, for example, by drilling each injection pipe 103 from the outer wall thereof.
The treating liquid is supplied from a treating liquid source 130 to the proximal ends 101 of injection pipes 103 through a treating liquid supply pipe 120. Each injection pipe 103 has, at the proximal end 101 thereof, a liquid inlet 101a for introducing the treating liquid into a pipe portion (liquid jetting pipe portion) 104 defining the jet bores 102, and a joint 101b for coupling to the supply pipe 120.
The treating tank 110 supports a plurality of wafers W arranged therein. These wafers W receive a predetermined treatment as immersed in the treating liquid jetting from the jet bores 102 of injection pipes 103 and forming upward streams throughout the treating tank 110.
In an etching process, for example, a plurality of wafers W are immersed in deionized water jetting from the jet bores 102 of injection pipes 103 and filling the treating tank 110. Then, a chemical solution such as of hydrofluoric acid having etching action is jetted from the jet bores 102 of injection pipes 103 to replace the deionized water in the treating tank 110.
The chemical solution is jetted from the jet bores 102 of injection pipes 103 to form streams of the chemical solution throughout the treating tank 110. In this way, the deionized water is efficiently replaced by the chemical solution in the treating tank 110.
However, the treating liquid injection pipes 103 used conventionally have a drawback that marked variations occur in the head length of the treating liquid jetting from the jet bores 102. As shown in FIG. 2, the head lengths wl of the treating liquid jets increase gradually from the jet bore 102 adjacent the proximal end 101 to the jet bore 102 adjacent the distal end 100 of each injection pipe 103. FIG. 2 schematically shows results of an experiment carried out by using injection pipes 103 having an inside diameter id of 16 mm, and introducing the treating liquid at a flow rate of 10 l/min. through the liquid inlets 101a. Line wlt in FIG. 2 represents a head length of the treating liquid jetting from the jet bores 102 closest to the distal ends 100.
Thus, in an etching process performed in the conventional treating tank 110, for example, the deionized water cannot be replaced uniformly by the chemical solution in the treating tank 110 because of the variations in the head length wl of the treating liquid jetting from the jet bores 102. As shown in FIG. 1B, for example, when a plurality of wafers W are treated simultaneously as immersed in the treating liquid, the wafers W arranged adjacent the distal ends 100 and those arranged adjacent the proximal ends 101 of treating liquid injection pipes 103 are etched in different amounts. With such variations, it has been impossible to treat the wafers W uniformly.